Semi-automatic firearms are designed to fire a round of ammunition, such as a cartridge or shot shell, in response to each squeeze of the trigger of the firearm, and thereafter automatically load the next shell or cartridge from the firearm magazine into the chamber of the firearm. During firing, the propellant inside the round is ignited, producing an expanding column of high pressure gases within the chamber and barrel of the firearm. The force of this expanding gas propels the bullet/shot of the round of ammunition down the barrel.
In some types of semi-automatic firearms, including rifles, shotguns, and some handguns, a portion of the expanding gases will be directed through a duct or port that interconnects the barrel of the firearm to a gas operating system, such as a piston assembly that houses an axially moveable gas piston, or a gas impingement system that redirects a portion of the expanding gases to impinge on the bolt assembly within a receiver of the firearm. The barrel and the gas operating system typically are coupled to the receiver of the firearm, with the gas operating system acting to cause the rearward motion of the bolt assembly, which in turn opens the chamber and causes the empty shell or cartridge casing to be ejected and thereafter, as the bolt assembly moves forwardly, a next round is loaded into the chamber, after which the bolt is returned to a locked position for firing as the expanding gases dissipate or are bled off.
In addition, during firing it is possible for a cartridge or round of ammunition in the firearm chamber to fail. Given the high pressures generated upon firing, especially when using higher power cartridges, such failures can cause gas pressure to build up in the chamber and/or the upper receiver. Such gases generally will be hot and under substantially high pressure, and thus can force unburned propellant, combustion residue, metal pieces and other debris from the failed cartridge, and/or other hazardous materials, out of the firearm in unpredictable trajectories. Consequently, it is desirable to protect a user from such high pressure gases venting from the firearm in the case of a cartridge failure.
Accordingly, it can be seen that a need exists for gas venting features for a firearm chamber that addresses the foregoing and other related and unrelated problems in the art.